1. Field of the Invention
The invention relates to engineered transporter proteins comprising at least one fluorescent reporter covalently bound to the transporter protein, wherein the transporter proteins of the present invention comprise a structural inverted repeat motif, with the motif comprising a first and second subunit that are structural inverted repeats of one another and that are joined to one another by a polypeptide loop.
2. Background of the Invention
Transporter proteins are membrane bound proteins that often utilize potential gradients to drive transport of molecules and ions into and out of cells. Traditionally, these proteins are classified based on the similarity of their amino acid sequence, i.e., the primary structure of the protein.
There is, however, an understanding of the three-dimensional structure of some of these transporters that is emerging. Indeed, some of these transporter proteins possess a structural inverted repeat, and transporters proteins with apparently disparate amino acid sequences have been shown to assume such a structure. It was not at all understood how this structural inverted repeat may affect the molecule or ion flux that is associated with these proteins.
Voltage sensors have been generated by others based on, for example, potassium channels, but these voltage sensors do not directly measure potassium transport. Instead these voltage sensors merely measure membrane potential using the voltage sensor of the transporter. To date, there has been no way to monitor or directly measure molecule or ion transport.
The present invention solves the problems by providing transport proteins that are capable of signaling a conformational change during the transport process. The invention thus provides sensors that are based on virtually any transporter with the required three-dimensional conformation, which, in turn, provides a new means of monitoring their activity or modifications by the regulatory machinery in real time in vivo